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Compton scattering (or the Compton effect) is the quantum theory of high frequency photons scattering following an interaction with a charged particle, usually an electron. Specifically, when the photon hits electrons, it releases loosely bound electrons from the outer valence shells of atoms or molecules.
A gamma ray cross section is a measure of the probability that a gamma ray interacts with matter. The total cross section of gamma ray interactions is composed of several independent processes: photoelectric effect, Compton (incoherent) scattering, electron-positron pair production in the nucleus field and electron-positron pair production in the electron field (triplet production).
The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, solid state, and quantum chemistry to draw inferences about the properties of atoms, molecules and ...
Compton effect. Incident photon (with wavelenghth λ) hits an electron in a target.This produces a scattered photon (with wavelenghth λ ' >λ) and a recoil electron.. In 1923, Arthur Compton had shown experimentally that x-rays were scattered elastically by free electrons, in accordance to the conservation of energy. [1]
The total absorption coefficient of aluminium (atomic number 13) for gamma rays, plotted versus gamma energy, and the contributions by the three effects. As is usual, the photoelectric effect is largest at low energies, Compton scattering dominates at intermediate energies, and pair production dominates at high energies.
The formula describes both the Thomson scattering of low energy photons (e.g. visible light) and the Compton scattering of high energy photons (e.g. x-rays and gamma-rays), showing that the total cross section and expected deflection angle decrease with increasing photon energy.
Unlike the photoelectric effect, the absorption resulting from Compton scattering is independent of the atomic number of the atoms present in the crystal, but linearly on their density. At γ-ray energies higher than E γ {\displaystyle E_{\gamma }} > 1022 keV, i.e. energies higher than twice the rest-mass energy of the electron, pair ...
This was an important discovery during the 1920s when the particle (photon) nature of light suggested by the photoelectric effect was still being debated, the Compton experiment gave clear and independent evidence of particle-like behavior. [25] [30] The formula describing the Compton shift in the wavelength due to scattering is given by: